Fwd: [ironic] [tripleo] RFC: lzma vs gzip for compressing IPA initramfs

[Dmitry Tantsur]

FYI folks. I know that the image size has been a recurring issue.

---------- Forwarded message ---------
From: Dmitry Tantsur <dtan...@redhat.com>
Date: Thu, Nov 26, 2020 at 5:54 PM
Subject: [ironic] [tripleo] RFC: lzma vs gzip for compressing IPA initramfs
To: openstack-discuss <openstac...@lists.openstack.org>

Hi folks,

I've been playing with ways to reduce the size of our IPA images. While package removals can only save us tens of megabytes, switching from gzip to lzma reduces the size by around a third (from 373M to 217M in my testing).

What's the caveat? The unpacking time increases VERY substantially. On my nested virt lab the 217M image took around 5 minutes to unpack. I'm not sure how much it will impact real bare metal, please feel free to test https://review.opendev.org/c/openstack/ironic-python-agent-builder/+/764371 and tell me.

So, what do you think? Switching to lzma by default will likely affect CI run time (assuming we still have DIB jobs somewhere...) and development environments, but it will also provide a visible reduction in the image size (which benefit all environments). Large TripleO images may particularly benefit from this (but also particularly affected by the unpacking time).

Feedback is very welcome.

Dmitry

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Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn,
Commercial register: Amtsgericht Muenchen, HRB 153243,
Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill

[Kevin Fox]

Since it varies so widely in size and CPU time, would it be reasonable to make it configurable and support both?

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[Dmitry Tantsur]

Given how metal3 is designed, we'll need to ship both then?